INTRODUCTION. XXxili 
north, Down with 957 sq. miles has 768, and Antrim with 1,191 
sq. miles a total of 777. This comparison, however, is less 
unfavourable when some of the western maritime counties are 
selected. Thus Donegal with 1,870 sq. miles has 752, both 
its area and flora being almost the same as Kerry ; Clare with 
1,348 sq. miles has a total of 773, and Cork, much the largest 
county in Ireland with 2,890 sq. miles, has 797. It will be 
seen from these figures that in comparing equal areas the flora 
of the west of Ireland is less varied, or in other words, poorer 
in species than the east. The botany of all these counties has 
now been pretty well investigated and it is unlikely that any 
additions to their plant lists will materially alter the figures 
given above. The real element of uncertainty, however, in 
all these numerical comparisons lies in the number of aliens 
admitted by different observers to the various county lists. 
Each one decides according to his personal bent the precise 
amount of naturalization that entitles an alien plant to be 
definitely included in the flora of a county, and probably no 
two observers would quite agree as to the exact standing of 
many of the claimants. 
An examination of the 762 species and subspecies included 
in the Kerry flora shows that while 652 of them may be 
regarded as native, 110, or just about one-seventh of the total, 
are classed as non-native, including in this latter group plants 
described as Denizens, Colonists or Aliens.* If these figures 
are compared with those given in the Flora of Dublin, a typical 
east coast county, it will be found that 162 out of 754, or rather 
more than a fifth of the whole, are included under these three 
heads. The comparative smallness of this introduced group in 
Kerry is a suggestive feature in its flora. No doubt the 
relative rarity of light soils and the smaller extent of cultiva- 
tion in this county, amounting to about 15 p.c. of the total area 
as compared with 30 p.c. in Dublin, accounts for portion of this 
difference, more especially in the Colonist group, but probably 
as potent a cause is to be found in the excessive humidity of 
the Kerry climate which appears in some way to repel this 
non-native group as strongly as it attracts the northern forms 
among the native flora. aod 
The profound influence exercised by humidity is clearly seen 
in the proportions which certain Orders, such as the Cyperacea, 
Filices and Naiadacee, bear to the Kerry flora when compared 
with the proportions borne by the same Orders to the floras of 
drier districts. In the following table the percentages for these 
* For definitions of these terms see p. lxx of this Introduction. 
